[Coco] Floppy - less boot , was Re: VI and VIRQ

[Robert Gault]

Diego Barizo wrote:
> My doubts come from the fact that, actually, I'm booting from a virtual 
> floppy in the HD.
> I thought that for the system, it would be just as booting from a real 
> diskette...
> How does it work in this case?
> 
> Diego
 ><snip>

For the Coco to be able to talk to hardware, in this case drives, it 
must use a driver that understands the language of the hardware. On your 
system you have floppies and a hard drive (either scsi or ide) and they 
don't speak the same language. Therefore you have two different drivers, 
one for the floppies and the other for the hard drive.

When you place an OS-9 boot disk on one of the RGBDOS/HDBDOS virtual 
Basic drives on the hard drive, that is not a floppy. You must use the 
driver for the hard drive to do I/O to the virtual floppy. That means 
the boot module on that drive must be one for hard drive use and OS9Boot 
must contain a driver and descriptor for hard drive use.

The process of booting requires track 34 be found and loaded into 
memory. This will be done by the HDBDOS driver in your new DOS chip. 
Once track 34 is loaded, the code there starts running and Boot takes 
over to load the file OS9Boot. Since this is on a virtual drive, you 
must have a Boot that speaks "hard drive". Once OS9Boot has been loaded 
into memory, the driver for hard drive use takes over and it must have a 
/dd which points to the hard drive.

The boot disk you described as using seems to have had the correct Boot 
module (although I'm not sure of this), had the correct driver in the 
OS9Boot file, but did not have a /dd pointing to the hard drive.
You should still have been able to complete the boot process if and only 
if the boot disk was in your floppy drive. That's because as soon as the 
code in OS9Boot started to run and looked for /dd, it would have seen 
that an 80 track double sided floppy should be used.